Rising expectation for public safety have prompted governmental agencies to review the regulations and legislation that pertain to the flammability and smoke hazards that are associated with ignited artificial polymeric materials. Particular emphasis has been directed to thermoplastic materials that are produced by rapid extrusion manufacturing processes. Commercially available fire retardants for extruded polymeric materials are primarily halogenated hydrocarbons and exhibit at least five major disadvantages: (1) they are intrinsically toxic, (2) they retard fire only after being vaporized by the action of heat, (3) they produce corrosive and highly toxic vapors, (4) they do not suppress smoke which is known to be a leading cause of death by fire, and (5) they often require the presence of antimony oxide which is now known to be a dangerous carcinogenic compound. To improve the situation, the United States National Materials Advisory Board has recommended the development of char forming fire retardants which reduce or eliminate all forms of vaporization upon exposure to fire.
Efforts have been made to develop non-halogenated hydrocarbon type fire retardants for extrudable thermoplastics. U.S. Pat. No. 4,174,343, issued November 13, 1979, W. B. Hardy et al., discloses a polyolefin composition containing, as a fire retardant, a combination of a disphosphonate, and ammonium polyphosphate. Also disclosed is a polyolefin composition containing 20-40 wt. % dicyanopentaerythritol diphosphonate. The retardant is especially used to render homopolypropylene flameretardant, but copolymers with 10-15% ethylene or (iso)butylene are also applicable.
U.S Pat. No. 4,312,802, granted January 26, 1982, G. Bertelli, discloses a self-extinguishing polymer composition comprising (a) 100 parts of a thermoplastic polymer, (b) 5 to 30 parts of an ammonium or aminophosphate and (c) 3 to 20 parts of an N-containing organic compound which on heating in the presence of component (b) forms a carbonaceous non-dripping mass. The fire retardant system can be used with olefin (co)polymers such as polypropylene, polyethylene, ethylene-propylene copolymers, polystyrene, ABS, polyethylene terephthalate, polybutylene terephthalate, polycarbonates and polyamides. They purportedly give good self-extinguishing properties and do not cause corrosion of processing apparatus or generate toxic smoke and gases on ignition.
British Pat. No. 1,603,123, granted November 18, 1981, Johnson Trading Co., discloses a flame-proofing and fireretarding composition comprising an aqueous solution of (a) ammonium hydrogen sulphate, (b) ammonium dihydrogen phosphate and (c) diammonium hydrogen phosphate. It can also be in the form of an anhydrous mixture for dissolution in water. The composition can contain a binder, for example, an alkali metal silicate (up to 1 wt. %); a water-repellant additive such as sodium stearate (up to 0.5 wt. %); an additional ammonium salt, for example, sulphamate or meta-borate (up to 4 wt.%); a hypochlorite salt (up to 0.01 wt. %); a chloride salt (wt. ratio of hypochlorite to chloride 1:8 to 20): and Na.sub.2 HP).sub.4. The composition is said to provide "balanced" protection against flame spread and melt whilst meeting health and hygiene requirements.
U.S. Pat. Nos. 2,287,597, 1943, 2,464,342, 1949, 2,514,268, 1950, and 2,536,988, 1951 disclose melamine containing fire retardants.